patch 9.0.1729: screenpos() wrong when w_skipcol and cpoptions+=n

Problem:    screenpos() wrong result with w_skipcol and cpoptions+=n
Solution:   Use adjust_plines_for_skipcol() instead of subtracting
            w_skipcol.

closes: #12625

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: zeertzjq <zeertzjq@outlook.com>
diff --git a/src/proto/misc1.pro b/src/proto/misc1.pro
index 5884821..b87b7ea 100644
--- a/src/proto/misc1.pro
+++ b/src/proto/misc1.pro
@@ -2,12 +2,12 @@
 int get_leader_len(char_u *line, char_u **flags, int backward, int include_space);
 int get_last_leader_offset(char_u *line, char_u **flags);
 int plines(linenr_T lnum);
-int plines_win(win_T *wp, linenr_T lnum, int winheight);
+int plines_win(win_T *wp, linenr_T lnum, int limit_winheight);
 int plines_nofill(linenr_T lnum);
-int plines_win_nofill(win_T *wp, linenr_T lnum, int winheight);
+int plines_win_nofill(win_T *wp, linenr_T lnum, int limit_winheight);
 int plines_win_nofold(win_T *wp, linenr_T lnum);
 int plines_win_col(win_T *wp, linenr_T lnum, long column);
-int plines_m_win(win_T *wp, linenr_T first, linenr_T last);
+int plines_m_win(win_T *wp, linenr_T first, linenr_T last, int limit_winheight);
 int gchar_pos(pos_T *pos);
 int gchar_cursor(void);
 void pchar_cursor(int c);